Slowing Down to Save Lives/The Impact of Traffic Calming Measures

Slowing Down to Save Lives/The Impact of Traffic Calming Measures

Traffic calming measures are essential tools in the quest for safer streets and communities. By implementing strategies such as speed humps, lower speed limits, and automated enforcement, cities aim to reduce the number of traffic-related injuries and fatalities. This article delves into the impact of these measures, examining their effectiveness in improving safety, the challenges they face, and the future directions of traffic safety initiatives like Vision Zero. Drawing on data and lessons learned from various urban environments, we explore how these interventions can create self-enforcing streets and contribute to sustainable safety for all road users.

Understanding Traffic Calming Measures

Defining Speed Humps and Bumps

Speed humps and bumps are traffic calming measures designed to slow down vehicles on roads, particularly in residential areas or near schools. Speed humps are generally wider and lower than speed bumps, providing a more gradual slowing of vehicles. They are often preferred in areas where a gentle deceleration is desired, such as near parks or hospitals. Speed bumps, on the other hand, are more abrupt and are typically used in parking lots or private driveways. They are higher and narrower, causing a more significant reduction in vehicle speed. Both speed humps and bumps can be made from various materials, including concrete, asphalt, and rubber, and come in different sizes to suit specific applications.
The design and installation of speed humps and bumps are crucial for their effectiveness. Uniform size and ease of installation are important factors to consider. Modular designs offer flexibility and can be adapted to different road conditions.
Here are some key differences between speed humps and bumps:
  • Speed humps are lower to the ground and less invasive, making them less of a hassle for snow removal.
  • Speed bumps are higher and can cause vehicles to scrape and ground out if not installed properly.
  • Installation time can vary, with an average 9ft long speed bump being installed within 2 hours.

The Role of Lower Speed Limits

The implementation of lower speed limits is a cornerstone of traffic calming strategies, aiming to enhance safety for all road users. Lower speed limits have been shown to significantly reduce the likelihood and severity of crashes. For instance, following the reduction of speed limits, New York City witnessed a remarkable decrease in traffic and pedestrian fatalities, with a 22% drop in traffic fatalities and a 25% fall in pedestrian deaths within just a year. Lower speed limits not only diminish the frequency of accidents but also encourage more responsible driving behavior. The National Highway Traffic Safety Administration (NHTSA) reports that these reductions were associated with a 50% reduction in fatal and injury crashes, a 26% reduction in total crashes, and an 18% reduction in property damage only (PDO) crashes. This data underscores the profound impact that speed limit adjustments can have on urban safety.
While the cost of comprehensive street redesigns can be prohibitive, the adoption of lower speed limits is a relatively low-cost intervention that can yield significant safety benefits when applied across an entire city.
However, the effectiveness of lower speed limits is contingent upon consistent enforcement and public acceptance. Without these, the potential safety gains may not be fully realized, leading to a patchwork of compliance and ongoing risks on the roads.

Automated Enforcement and Its Effectiveness

Automated enforcement, such as traffic safety cameras, has emerged as a critical tool in the quest to enhance road safety. Automated enforcement systems are designed to capture and deter dangerous driving behaviors, such as speeding and running red lights, without the need for police presence. These systems operate continuously, providing around-the-clock monitoring that a police officer cannot match. The effectiveness of automated enforcement is supported by data indicating a reduction in dangerous driving behaviors. For instance, the GHSA states that automated enforcement significantly lowers the instances of driving that result in fatalities. This is particularly important in areas where traditional policing may not be feasible or where it could lead to biased enforcement practices.
Automated enforcement works preemptively to prevent harm and creates safer conditions for all road users.
However, the implementation of automated enforcement is not without challenges. It requires careful planning and community engagement to ensure that it is used equitably and effectively. Moreover, it should be part of a broader strategy that includes street redesign and other systemic approaches to create self-enforcing streets that naturally discourage dangerous driving.

Analyzing the Impact on Safety

Reduction in Traffic and Pedestrian Fatalities

The implementation of traffic calming measures has led to a notable decrease in both traffic and pedestrian fatalities. A 29% reduction in pedestrian fatalities was observed in New York City from 2014 to 2023, highlighting the effectiveness of these interventions. Similarly, overall traffic fatalities saw a 16% decline over the same period, translating to more than 400 lives saved. Following the reduction of the citywide speed limit to 25 mph, a significant impact was seen: traffic fatalities declined by 22% and pedestrian fatalities by 25%. This demonstrates the direct correlation between lower speed limits and improved safety outcomes. Automated enforcement tools, such as speed safety cameras, also contributed to these results. In fiscal years 2021 and 2022, 92% of camera locations reported a decrease in speeding, with the number of citations dropping by an average of 35%, indicating a shift in driver behavior.
While the early years of Vision Zero in New York City showed promise with decreased fatalities, the challenge remains to sustain and scale these successes. The rise in fatalities in recent years underscores the need for continuous adaptation and commitment to traffic safety measures.
The cost-effective nature of certain interventions, like Leading Pedestrian Intervals (LPIs), which cost just $1,200 each, has also been crucial. At intersections with LPIs installed, there was a 34% decline in pedestrian deaths and serious injuries, and a 56% reduction in incidents involving left-turning vehicles hitting pedestrians or cyclists.

The Influence of Street Redesign

Street redesign plays a crucial role in traffic calming and subsequently in enhancing road safety. Narrowing vehicle travel lanes is a measure that has been shown to effectively reduce speeding and improve safety. An expansive study highlighted by Forbes suggests that, contrary to expectations, narrower lanes are often safer than wider ones in urban areas. This finding supports the notion that street redesign can influence driver behavior and contribute to safer city streets. Effective street redesigns incorporate various elements that work together to calm traffic. These include raised crosswalks, curb extensions, and daylighting at intersections. Such interventions are not only cost-effective but also operate continuously, reducing risk even when dangerous behaviors occur. The Vision Zero initiative emphasizes the importance of building self-enforcing streets that prioritize safety over enforcement. Despite the proven benefits of street redesign, implementation often remains inconsistent. Projects tend to be reactive, emerging in the wake of accidents, which leads to a patchwork of improvements across cities. To achieve equitable safety outcomes, it is essential to scale successful redesigns systemwide, ensuring that all neighborhoods benefit from these measures.

Behavioral Changes Among Drivers

Traffic calming measures not only alter the physical environment but also significantly influence driver behavior. The introduction of speed humps, lower speed limits, and automated enforcement has been shown to encourage more cautious driving. Drivers tend to adapt to these changes over time, resulting in a more consistent observance of speed limits and an overall reduction in aggressive driving maneuvers.
The consistent application of traffic calming strategies creates a culture of safety that permeates through the driving community, leading to long-term behavioral changes.
The following list highlights key behavioral changes observed among drivers in response to traffic calming measures:
  • Increased compliance with speed limits
  • Reduced instances of aggressive driving
  • Greater awareness of pedestrians and cyclists
  • More frequent yielding to right-of-way
  • Enhanced anticipation of potential road hazards
These changes contribute to the overarching goal of reducing traffic-related injuries and fatalities, demonstrating the profound impact that infrastructure and policy can have on driver behavior.

Challenges and Adaptations in Traffic Safety

Scaling Successes to Meet Urban Growth

As cities continue to expand and evolve, the need to scale traffic calming measures becomes increasingly critical. Urban growth demands a strategic approach to ensure that safety interventions keep pace with development. Successful traffic calming projects, such as raised crosswalks and narrow lanes, have proven effective in specific areas but face the challenge of being implemented citywide. To address this, cities must consider a variety of strategies:
  • Scale successful street redesign projects across different neighborhoods.
  • Redesign major arterial streets to be self-enforcing, with features like daylighting and curb extensions.
  • Expand automated safety technology to cover a wider range of infractions.
The goal is to create a consistent and equitable distribution of traffic calming measures throughout the city, rather than leaving them as piecemeal projects that only benefit certain areas.
By taking these steps, cities can work towards a more comprehensive and inclusive approach to traffic safety, one that accounts for the diverse needs of growing urban populations and the varying infrastructure of different neighborhoods.

Adapting to New Traffic Patterns and Vehicle Designs

As urban landscapes evolve, traffic patterns and vehicle designs undergo significant changes, necessitating adaptive traffic safety measures. The rise of larger vehicles, increased traffic, and a surge in cycling have all contributed to the need for dynamic safety interventions.
  • Larger vehicles, such as SUVs, have become more prevalent, requiring adjustments in road design to ensure visibility and pedestrian safety.
  • The growth in cycling popularity demands the expansion of bike lanes and the implementation of protective barriers.
  • Increased traffic volume calls for more sophisticated signal timing and intersection designs to manage flow and reduce congestion-related accidents.
Traffic safety measures must be fluid and responsive to the ever-changing dynamics of city streets. This includes not only the physical redesign of streetscapes but also the policies that govern traffic behavior.
Adaptations to new traffic patterns and vehicle designs are not just about reacting to changes; they are about anticipating future trends and preparing infrastructure to handle them safely. This proactive approach can help maintain the momentum of initial safety successes and prevent the plateauing or receding of safety gains over time.

Overcoming the Limitations of Selective Enforcement

Selective enforcement of traffic laws, relying on police presence to catch and penalize violators, faces inherent limitations. A single officer can only address one violation at a time, leading to a ‘whack-a-mole’ effect where overall safety may not improve. In contrast, systemic changes such as street redesigns and automated enforcement work around the clock to preemptively reduce risks.
Systemic approaches, including the creation of self-enforcing streets, offer a more equitable and effective solution. These measures ensure safety interventions are not limited to the presence of law enforcement, thereby avoiding biased enforcement practices.
To truly enhance urban traffic safety, a shift towards comprehensive, non-selective measures is essential. These include:
  • Scaling successful street redesign projects citywide
  • Implementing protected bike lanes to naturally slow traffic
  • Utilizing automated enforcement to consistently deter reckless driving
By focusing on these strategies, cities can create safer environments for all road users, reduce the need for selective enforcement, and foster sustainable safety improvements.

Creating Self-Enforcing Streets and Sustainable Safety

Designing Roads for Natural Speed Control

The concept of self-enforcing streets is central to natural speed control. By integrating physical design elements that inherently limit vehicle speed, the reliance on active enforcement is reduced. For instance, the introduction of protected bike lanes not only provides safety for cyclists but also narrows the roadway, which can lead to a natural reduction in vehicle speeds. Effective traffic calming measures are not just about installing speed bumps; they encompass a variety of interventions. These can range from the strategic lowering of speed limits to the retiming of traffic signals, each contributing to a safer road environment. The modular design of speed bumps allows for easy installation and adaptability, making them a flexible solution for different road types.
While high-cost interventions like complete street redesigns are impactful, it’s the cumulative effect of widespread, low-cost measures that can lead to significant improvements in road safety.
It’s crucial to apply these measures comprehensively across a city to avoid the ‘whack-a-mole’ effect, where safety issues are merely shifted from one area to another. Universal changes are necessary to create a consistent and predictable road environment that encourages safer driving behaviors.

The Role of Protected Bike Lanes in Traffic Calming

Protected bike lanes play a crucial role in the ecosystem of traffic calming measures. By their very design, they not only provide a safe space for cyclists but also inherently slow down vehicular traffic. The presence of these lanes can alter driver behavior, leading to a more cautious and moderated speed. The implementation of protected bike lanes has been shown to bring about a significant reduction in injuries and fatalities for all road users. This is not just a daytime phenomenon; the safety benefits extend throughout the hours of darkness as well, ensuring round-the-clock protection.
With limited resources, it is imperative that cities prioritize interventions that offer the most significant impact. Protected bike lanes stand out as a cost-effective solution that not only enhances safety but also encourages a shift from car dependency to more sustainable modes of transportation.
Here are some strategic steps cities can take to enhance traffic calming through protected bike lanes:
  • Decriminalize jaywalking and install Leading Pedestrian Intervals (LPIs) to complement bike lanes at busy intersections.
  • Redirect funds from public education campaigns to the construction of safe infrastructure, including protected bike lanes.
  • Set ambitious targets for reducing vehicle miles traveled to encourage a shift towards safer and more sustainable travel modes.
  • Fully implement comprehensive street plans that focus on equity and connectivity, expanding protected bike lanes and bus-only lanes.

The Impact of Comprehensive Citywide Changes

The adoption of comprehensive citywide changes in traffic safety has marked a significant shift in urban policy, emphasizing the protection of all citizens and the promotion of safer streets. Systemwide interventions have been crucial in altering driver behavior and enhancing pedestrian visibility, particularly through cost-effective measures such as leading pedestrian intervals at traffic lights.
The success of these changes hinges on their universal application, ensuring that safety is not a privilege but a standard across the cityscape.
The following table highlights key initiatives and their outcomes in New York City:
Initiative Description Outcome
Leading Pedestrian Intervals Gives pedestrians a head start at traffic lights Increased pedestrian visibility
34th Avenue Open Street Street redesign for pedestrian priority Reduced traffic violations
14th Street Busway Bus priority corridor Improved public transit efficiency
  These initiatives, among others, demonstrate the potential of a holistic approach to traffic safety. By scaling successful projects and redesigning streets to be naturally self-enforcing, cities can address the challenges posed by increased vehicle size and power, as well as the rise in pedestrian and cyclist road use. The future of urban traffic safety lies in the ability to adapt to changing conditions and to implement layered strategies that cater to the evolving needs of a dynamic city environment.


The evidence is clear: traffic calming measures like speed humps and speed bumps are not just road fixtures—they are lifesavers. The implementation of such measures, along with comprehensive strategies like Vision Zero, has shown a significant reduction in traffic and pedestrian fatalities. Cities that have embraced systemwide safety interventions, such as lowering speed limits and installing automated enforcement, have witnessed a decline in speeding and subsequent accidents. However, the journey doesn’t end with initial success. As urban landscapes and traffic dynamics evolve, so must our approach to traffic safety. Adapting to changing conditions, making low-cost safety changes universal, and building self-enforcing streets are crucial steps in maintaining and improving upon the gains achieved. It’s not just about celebrating the victories but also about recognizing and addressing the shortcomings to ensure that traffic safety is a dynamic and sustained effort. Ultimately, saving lives on our streets requires a persistent commitment to action, innovation, and the unwavering resolve of city officials and community members alike.